Bovine fibroblasts in long‐term tissue culture: Chromosome studies

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Abstract
Three fibroblastic strains of fetal calf lung origin have been grown in vitro in serial culture. Chromosome alterations were found in all three. In early passages the cells remained diploid without chromosome changes. After this period cells started to become hypodiploid until they were all abnormal. The decrease in the counts was caused by a process interpreted as a fusion or association of telocentric elements. In the process telocentric chromosomes were randomly joined two and two at the centromere forming single biarmed chromosomes. No loss of detectable chromatid material accompanied the apparent fusion. No cytological changes were observed in the cultures at this stage.Around passage 70, additional abnormalities began to appear. Severe chromosome alterations were observed with aneuploidy, widely scattered counts dominated by hypotetraploid numbers, breaks, dicentric forms and various other rearrangements. This change was accompanied by a decreased growth rate and degenerative cytological changes in the cultures analogous to those described in human and hamster fibroblasts approaching the end of their finite life span in vitro.